Electronic device, piezoelectric device, liquid ejecting head, and manufacturing methods for electronic device, piezoelectric device, and liquid ejecting head

ABSTRACT

An electronic device includes a capacitor that is configured with a first electrode layer, an insulating layer, and a second electrode layer being formed in the order listed herein. At least one end of the capacitor is defined by an end of the second electrode layer. The insulating layer is provided so as to extend to a non-element region that is on the outside of one end of the capacitor. The insulating layer under the non-element region is formed thinner than the insulating layer under the capacitor. A difference between the thickness of the insulating layer under the non-element region and the thickness of the insulating layer under the capacitor is equal to or less than 50 nm.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/614,889, filed Jun. 6, 2017 which is a continuation of U.S.application Ser. No. 15/240,864, filed Aug. 18, 2016, and issued as U.S.Pat. No. 9,694,580 on Jul. 4, 2017, which claims priority to JapanesePatent Application No: 2015-165506, filed Aug. 25, 2015, all of whichare expressly incorporated by reference herein in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to an electronic device that includes afirst electrode layer, a second electrode layer and an insulating layerwhich is interposed between the first electrode layer and the secondelectrode layer, a piezoelectric device, a liquid ejecting head, andmanufacturing methods for the electronic device, the piezoelectricdevice and the liquid ejecting head.

2. Related Art

An electronic device provided with a capacitor, such as a piezoelectricelement and the like, in which an insulating layer is interposed betweenelectrodes, has been used in a variety of apparatuses, sensors, or thelike. For example, in a liquid ejecting apparatus, the piezoelectricelement that is provided in the piezoelectric device, which is a type ofthe electronic device, is used to eject (discharge) a variety of liquidsfrom a liquid ejecting head. The example of the liquid ejectingapparatus includes an image recording apparatus, such as an ink jetprinter or an ink jet plotter. Recently, however, the liquid ejectingapparatus has also been applied to a variety of manufacturingapparatuses by taking advantage of a feature that allows an extremelysmall amount of liquid to be accurately targeted at a predeterminedposition. For example, the liquid ejecting apparatus is applied to adisplay manufacturing apparatus that manufactures a color filter of aliquid crystal display and the like, an electrode forming apparatus thatforms an electrode an organic electroluminescent (EL) display, a fieldemission display (FED), and the like, and a chip manufacturing apparatusthat manufactures a biochip (biochemical element). A recording head forthe image recording apparatus ejects liquid ink, and a colorant ejectinghead for the display manufacturing apparatus ejects solutions ofrespective colorants of red (R), green (G) and blue (B). In addition, anelectrode material ejecting head for the electrode forming apparatusejects liquid electrode materials, and a bioorganic material ejectinghead for the chip manufacturing apparatus ejects solutions of liquidbioorganic materials.

The capacitor is formed by a lower electrode layer that is made ofmetal, a piezoelectric layer made of a piezoelectric body, such as leadzirconate titanate (PZT) and the like, and an upper electrode layer madeof metal being sequentially stacked onto a substrate. Such a capacitorfunctions as the piezoelectric element, and the capacitor is bent anddeformed once an electric field, which is generated due to the potentialdifference between both electrodes, is imparted between the lowerelectrode layer and the upper electrode layer. Each of the layers thatconfigure such a piezoelectric element is formed, as in JP-A-2015-99864,for example, by etching being performed after each of the layers ofmetal or a piezoelectric body is made on the substrate, with a patternedresistant layer being used as a mask.

There are some piezoelectric elements in which one end of the lowerelectrode layer and one end of the piezoelectric layer are provided soas to extend to the outside of the upper electrode layer, and an end ofthe piezoelectric element is defined by the one end of the upperelectrode layer. In such a configuration, at a time when removing theupper electrode layer that is in the outside of the piezoelectricelement by etching, so-called over-etching, in which etching iscontinuously performed even after an amount that is equal to thethickness of the upper electrode layer has been removed, is performed toavoid a short circuit caused by the upper electrode layer not beingcompletely removed. Accordingly, part of the piezoelectric layer isremoved. However, if the part of the piezoelectric layer is removedexcessively by the over-etching, damage to a boundary of the one end ofthe piezoelectric element is likely to occur. It is estimated that suchdamage can occur even at the end of the capacitor which is formed of apair of upper and lower electrode layers and an insulating layerinterposed therebetween.

SUMMARY

An advantage of some aspects of the invention is to provide anelectronic device that includes a capacitor which is provided with afirst electrode layer, an insulating layer, and a second electrodelayer, and in which an end of the capacitor is defined by an end of thesecond electrode layer and damage to the end of the capacitor isprevented, a piezoelectric device, a liquid ejecting head, andmanufacturing methods for the electronic device, the piezoelectricdevice and the liquid ejecting head.

According to an aspect of an invention, there is provided an electronicdevice including a capacitor that is configured with a first electrodelayer, an insulating layer, and a second electrode layer being formed inthe order listed herein. At least one end of the capacitor is defined byan end of the second electrode layer. The insulating layer is providedso as to extend to a non-element region that is on the outside of oneend of the capacitor. The insulating layer under the non-element regionis formed thinner than the insulating layer under the capacitor. Adifference between the thickness of the insulating layer under thenon-element region and the thickness of the insulating layer under thecapacitor is equal to or less than 50 nm.

According to this configuration, it is possible to prevent thecapacitor, that is, the end of the capacitor which is defined by the endof the second electrode layer, from being damaged by excessiveover-etching. As a result, the reliability of the capacitor is improved,resulting in improved reliability of the electronic device.

According to another aspect of the invention, there is provided apiezoelectric device in which, in the electronic device of the aboveconfiguration, the insulating layer is a piezoelectric layer, and thecapacitor is a piezoelectric element.

According to this configuration, it is possible to prevent thepiezoelectric element, that is, an end of the piezoelectric elementwhich is defined by an end of the second electrode layer, from beingdamaged by excessive over-etching. As a result, the reliability of thepiezoelectric element is improved, resulting in improved reliability ofthe piezoelectric device.

According to still another aspect of the invention, there is provided aliquid ejecting head including: the piezoelectric device of the aboveconfiguration; a pressure chamber of which a volume is changed,following deformation of the piezoelectric element; and a nozzle thatcommunicates with the pressure chamber.

According to this configuration, the reliability of the liquid ejectinghead is improved.

According to still another aspect of the invention, there is provided amanufacturing method for an electronic device including a capacitor thatis configured with a first electrode layer, an insulating layer, and asecond electrode layer being formed in the order listed herein. Themanufacturing method for an electronic device includes etching thesecond electrode layer to remove the second electrode layer andcontinuously etching the insulating layer in a non-element region thatis on the outside of at least one end of the capacitor defined by an endof the second electrode layer generated by the etching of the secondelectrode layer even after the removal of the second electrode layer,such that the insulating layer under the non-element region is removedby 50 nm or less in a thickness direction.

According to this method, it is possible to manufacture, at a high yieldrate, the capacitor in which damage to the end of the second electrodelayer is prevented. That is, it is possible to efficiently manufacturethe electronic device with improved reliability.

According to still another aspect of the invention, there is provided amanufacturing method for a piezoelectric device in which, in theaforementioned manufacturing method for an electronic device, theinsulating layer is a piezoelectric layer, and the capacitor is apiezoelectric element.

According to this method, it is possible to manufacture, at a high yieldrate, the piezoelectric element in which the damage to the end of thesecond electrode layer is prevented. That is, it is possible toefficiently manufacture the piezoelectric device with improvedreliability.

According to still another aspect of the invention, there is provided amanufacturing method for a liquid ejecting head including: theaforementioned manufacturing method for a piezoelectric device; forminga pressure chamber of which a volume is changed, following deformationof the piezoelectric element; and forming a nozzle plate where a nozzlethat communicates with the pressure chamber is formed.

According to this method, it is possible to efficiently manufacture theliquid ejecting head with improved reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is perspective view illustrating a configuration of a printer.

FIG. 2 is an enlarged sectional view of main parts of a recording head.

FIG. 3 is an enlarged sectional view of main parts of a piezoelectricdevice.

FIG. 4 is an enlarged sectional view of main parts of a piezoelectricelement.

FIG. 5 is a graph illustrating a relationship between an amount ofover-etching performed on a piezoelectric layer and a defect rate of thepiezoelectric element.

FIGS. 6A to 6D are sectional views illustrating a piezoelectric elementmanufacturing method.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the invention will be described withreference to the accompanying drawings. The embodiment below isdescribed as if there are various limitations to the invention, but thefollowing description is merely a preferable and specific example, andthe scope of the invention is not limited to the forms described belowinsofar as there is no particular description to limit the spirit of theinvention. An ink jet recording head (hereinafter, a recording head)that is a type of a liquid ejecting head provided with a piezoelectricdevice which is a type of an electronic device according to theinvention, and an ink jet printer (hereinafter, a printer) that is atype of a liquid ejecting apparatus in which the ink jet recording headis mounted will be described as an example.

A configuration of a printer 1 will be described with reference toFIG. 1. The printer 1 is an apparatus that ejects ink (a type of liquid)with respect to a surface of a recording medium 2 (a type of targetedobject), such as recording paper and the like, to record an image or thelike. The printer 1 includes a recording head 3, a carriage 4 to whichthe recording head 3 is attached, a carriage moving mechanism 5 thatmoves the carriage 4 in a main scanning direction, and a transportingmechanism 6 that sends the recording medium 2 in a sub-scanningdirection. The ink is stored in an ink cartridge 7 which is a source forliquid. The ink cartridge 7 is detachably mounted with respect to therecording head 3. A configuration in which an ink cartridge is disposedon a side of a printer main body and the ink is supplied through an inksupplying tube from the ink cartridge to a recording head can beadopted.

The carriage moving mechanism 5 is provided with a timing belt 8. Thetiming belt 8 is driven by a pulse motor 9, such as a DC motor and thelike. Once the pulse motor 9 is operated, the carriage 4 reciprocates inthe main scanning direction (in a width direction of the recordingmedium 2) after being guided by a guide rod 10 that is built into theprinter 1. The position of the carriage 4 in the main scanning directionis detected by a linear encoder (not illustrated) that is a type ofposition information detecting means. The linear encoder transmits adetection signal, that is, an encoder pulse (a type of positioninformation), to a control unit of the printer 1.

Hereinafter, the recording head 3 will be described. FIG. 2 is anenlarged sectional view of main parts of the recording head 3. FIG. 3 isan enlarged sectional view of main parts of a piezoelectric device 14that is a type of electronic device. FIG. 4 is an enlarged sectionalview of main parts of a piezoelectric element 32 that is a type ofcapacitor. In this embodiment, the recording head 3 is attached to ahead case 16, in a state where the piezoelectric device 14 and a flowpath unit 15 are stacked, as illustrated in FIG. 2. For convenience ofdescription, a direction in which each member is stacked will bereferred to as an up-and-down direction.

The head case 16 is a box-shaped member made of a synthetic resin, and aliquid introduction path 18 is formed in the head case 16. The liquidintroduction path 18, just as a common liquid chamber 25 that will bedescribed later, is a space where ink common to a plurality of pressurechambers 30 that are arranged in parallel is stored. An upper end of theliquid introduction path 18 communicates with the ink cartridge 7 via aliquid path (not illustrated). At a lower end of the head case 16, thereis a housing space 17 for housing the piezoelectric device 14. Once theflow path unit 15 is bonded in a state of being positioned below a lowersurface of the head case 16, the piezoelectric device 14 that is stackedon the flow path unit 15 (communication substrate 24) is housed in thehousing space 17. Inside the head case 16, a penetration space 19 thatpenetrates the head case 16 in a height direction of the head case 16 isformed. A wiring member such as a flexible cable (not illustrated) thatsupplies a drive signal to the piezoelectric element 32 is disposed inthe penetration space 19.

The flow path unit 15 includes a nozzle plate 21 in which a plurality ofnozzles 22 are installed in a column-shape, and the communicationsubstrate 24 in which the common liquid chamber 25 or the like isprovided. The plurality of nozzles 22, from the nozzle 22 on one end tothe nozzle 22 on the other end, which are installed in a column-shape(nozzle column), are provided at regular intervals, that is, at a pitchcorresponding to a dot formation density. The common liquid chamber 25is a flow path common to the plurality of pressure chambers 30, and isformed to have a large length in a direction of the pressure chambers 30that are being arranged in parallel. Each of the pressure chambers 30communicates with the common liquid chamber 25 via an individualcommunication path 26 that is formed in the communication substrate 24.In other words, the ink in the common liquid chamber 25 is distributedto each of the pressure chambers 30 via the individual communicationpath 26. The nozzle 22 communicates with the corresponding pressurechamber 30 via a nozzle communication path 27 that has penetrated thecommunication substrate 24 in a thickness direction thereof.

In the embodiment, the piezoelectric device 14 is an electronic deviceformed by a pressure chamber formation substrate 29, a diaphragm 31, thepiezoelectric element 32 and a sealing plate 33 being stacked so as tobe made as a single unit, as illustrated in FIGS. 2 and 3. Thepiezoelectric device 14 has a size that allows it to be housed in thehousing space 17. Hence, the piezoelectric device 14 is housed in thehousing space 17.

The pressure chamber formation substrate 29 is a hard plate made ofsilicon, and in this embodiment, the pressure chamber formationsubstrate 29 is formed of a silicon single substrate of which surfaces(upper surface and lower surface) have a plane orientation of (110)plane. In the pressure chamber formation substrate 29, a plurality ofspaces that should become the pressure chambers 30, which are formed bycompletely removing parts of the pressure chamber formation substrate 29by etching in the thickness direction thereof, are arranged in parallelin a nozzle column direction. The lower sides of these spaces arepartitioned by the communication substrate 24, and the upper sides arepartitioned by the diaphragm 31, thereby forming the pressure chambers30. These spaces, that is, the pressure chambers 30, are long in adirection orthogonal to the nozzle column direction. In addition, oneend of each of the pressure chambers 30 in a longitudinal directioncommunicates with the individual communication path 26, and the otherend communicates with the nozzle communication path 27.

The diaphragm 31 is an elastic film-like member, and is stacked on theupper surface (surface on a side opposite to a communication substrate24 side) of the pressure chamber formation substrate 29. The diaphragm31 seals an upper opening of the space that should become the pressurechamber 30. In other words, the upper surface of the pressure chamber 30is partitioned by the diaphragm 31. Part of the diaphragm 31corresponding to the pressure chamber 30 (specifically, the upperopening of the pressure chamber 30) functions as a displacement portionthat is displaced in a direction separating away from the nozzle 22 orin a direction approaching the nozzle 22, following bending deformationof the piezoelectric element 32. That is, a region of the diaphragm 31corresponding to the upper opening of the pressure chamber 30 is a driveregion that allows the bending deformation. The deformation(displacement) of the drive region (displacement portion) changes thevolume of the pressure chamber 30. A region of the diaphragm 31 which isaway from the upper opening of the pressure chamber 30 is a non-driveregion where the bending deformation is inhibited.

The diaphragm 31 is made of, for example, a silicon dioxide (SiO₂)elastic film that is formed on the upper surface of the pressure chamberformation substrate 29, and a zirconium dioxide (ZrO₂) insulating filmthat is formed on the elastic film. The piezoelectric element 32 isstacked on a region (that is, the drive region) of the insulating film(surface of the diaphragm 31 on a side opposite to the pressure chamberformation substrate 29 side) corresponding to each of the pressurechambers 30. A configuration in which a pressure chamber formationsubstrate and a diaphragm are integrated with each other can be adopted.That is, a configuration can be adopted, in which etching processing isperformed, to form a pressure chamber, on a lower surface of thepressure chamber formation substrate until a thin portion that has asmall thickness is left on the upper surface, and the thin portionfunctions as the diaphragm.

In this embodiment, the piezoelectric element 32 is a piezoelectricelement in a so-called bending mode. The plurality of piezoelectricelements 32 are arranged in parallel, corresponding to each of thenozzles 22, in the nozzle column direction. As illustrated in FIGS. 3and 4, each of the piezoelectric elements 32 is formed, for example, bya lower electrode layer 37 (corresponding to a first electrode layer inthe invention), a piezoelectric layer 38 that is a type of an insulatinglayer, and an upper electrode layer 39 (corresponding to a secondelectrode layer in the invention) being sequentially stacked on thediaphragm 31. In this embodiment, the lower electrode layer 37 functionsas an individual electrode for each of the piezoelectric elements 32,and the upper electrode layer 39 functions as an electrode common toeach of the piezoelectric elements 32. A configuration can be adopted,in which the functions of the lower electrode layer 37 and the upperelectrode layer 39 are reversed depending on circumstances regarding adrive circuit or wiring. Once an electric field, which is generated dueto the potential difference between both electrodes of the lowerelectrode layer 37 and the upper electrode layer 39, is imparted to thepiezoelectric element 32 having such a configuration, the piezoelectricelement 32 is bent and deformed in the direction separating away fromthe nozzle 22 or in the direction approaching the nozzle 22. That is, aregion where the piezoelectric layer 38 is interposed between the lowerelectrode layer 37 and the upper electrode layer 39 is the piezoelectricelement 32 which is driven by the drive signal.

As illustrated in FIG. 3, the piezoelectric layer 38 is provided so asto extend to the non-element region 41 that is on the outside of theregion which is corresponding to the pressure chamber 30 in thedirection orthogonal to the nozzle column direction and which willbecome the piezoelectric element 32. Specifically, one end of thepiezoelectric layer 38 (left side in FIG. 3) is provided so as to extendbeyond one end of the lower electrode layer 37 to an end of the pressurechamber formation substrate 29 in the direction orthogonal to the nozzlecolumn direction. The other end of the piezoelectric layer 38 (rightside in FIG. 3) is on the outside of the sealing plate 33 beyond theother end of the upper electrode layer 39, and is provided so as toextend to a terminal region (not illustrated) corresponding to thepenetration space 19 of the head case 16, in the direction orthogonal tothe nozzle column direction. In the piezoelectric layer 38 which is onthe outside of the other end of the upper electrode layer 39, a contacthole 42 that penetrates the piezoelectric layer 38 in the thicknessdirection is formed. In this embodiment, the piezoelectric layer 38 isformed over the plurality of the piezoelectric elements 32 in the nozzlecolumn direction, and an opening (not illustrated) is formed in a partcorresponding to a region interposed between adjacent pressure chambers30, that is, a part corresponding to the non-drive region between thenearby pressure chambers 30. This opening is a concave portion or athrough-hole formed by removing a part of the piezoelectric layer 38,and extends along edges of the pressure chambers 30. That is, in aconfiguration where the opening is provided in such a manner, abeam-shaped piezoelectric layer 38 that is provided in a regioncorresponding to the pressure chamber 30, which is a part betweenadjacent openings in the nozzle column direction, and the upper andlower electrode layers 39 and 37, between which the piezoelectric layer38 is interposed, functions as the piezoelectric element 32.

As illustrated in FIG. 3, the one end of the lower electrode layer 37 inthe direction orthogonal to the nozzle column direction is formed on theinside of one end of the piezoelectric layer 38 and one end of the upperelectrode layer 39 in the aforementioned direction. Accordingly, one endof the piezoelectric element 32 in the direction orthogonal to thenozzle column direction is defined by the one end of the lower electrodelayer 37. In this embodiment, the one end of the lower electrode layer37 is provided so as to extend to a side which is slightly outside theregion corresponding to the pressure chamber 30. The other end of thelower electrode layer 37 in the direction orthogonal to the nozzlecolumn direction is provided so as to extend beyond the other end of theupper electrode layer 39 to the non-element region 41 in the directionorthogonal to the nozzle column direction. A lead electrode layer 44 isconnected, via the contact hole 42, to the lower electrode layer 37which is on the outside of the other end of the upper electrode layer39. The lead electrode layer 44 is provided so as to extend to theterminal region in the direction orthogonal to the nozzle columndirection on the piezoelectric layer 38, and is connected to a terminalcorresponding to the wiring member in the terminal region.

The upper electrode layer 39 is formed over the plurality of thepiezoelectric elements 32 in the nozzle column direction. As illustratedin FIG. 3, the one end of the upper electrode layer 39 in the directionorthogonal to the nozzle column direction is provided so as to extendbeyond the one end of the lower electrode layer 37 in the aforementioneddirection to the end of the pressure chamber formation substrate 29. Theother end of the upper electrode layer 39 in the direction orthogonal tothe nozzle column direction is formed on a side which is slightly insidethe other end of the lower electrode layer 37 and the piezoelectriclayer 38 in the aforementioned direction. Accordingly, the other end ofthe piezoelectric element 32 in the direction orthogonal to the nozzlecolumn direction is defined by the other end of the upper electrodelayer 39. In this embodiment, the other end of the upper electrode layer39 is provided so as to extend to a side which is slightly outside theregion corresponding to the pressure chamber 30.

Platinum (Pt), iridium (Ir), gold (Au), nickel (Ni), copper (Cu),chromium (Cr), titanium (Ti), tungsten (W), tantalum (Ta), zirconium(Zr), oxides of these chemical elements, and electrically conductiveoxides, including LaNiO₃, SrTiO₃, InSnO₃, and the like, are used in thelower electrode layer 37, the upper electrode layer 39, and the leadelectrode layer 44. In this embodiment, iridium (Ir), titanium (Ti),platinum (Pt) and oxides of these chemical elements are used in thelower electrode layer 37, and iridium (Ir), titanium (Ti) and oxides ofthese chemical elements are used in the upper electrode layer 39. Solidsolution of Pb(Zr,Ti)O₃, solid solution of Pb(MnNb)O₃—PbTiO₃, the solidsolutions being added with trace amounts of metallic elements, anddielectrics that do not contain lead (Pb), such as solid solution ofBi(FeMn)O₃—BaTiO₃, solid solution of K(NaNb)O₃ and the like, are used inthe piezoelectric layer 38. In this embodiment,Pb_(1.1)(Zr_(0.5)Ti_(0.5))O₃ are used in the piezoelectric layer 38. Asubstrate having a thickness of approximately 150 nm to 10 um can beused as the piezoelectric layer 38, depending on the purpose.

As illustrated in FIG. 4, the piezoelectric layer 38 under thenon-element region 41 which is on the outside of the other end of theupper electrode layer 39 is formed thinner than the piezoelectric layer38 under the piezoelectric element 32 by the upper electrode layer 39being removed and by over-etching (etching which is performedcontinuously even after the removal of the upper electrode layer 39)being performed when the piezoelectric element 32 is present. That is,the piezoelectric layer 38 under the non-element region 41 has been dugby the over-etching. In this embodiment, a boundary surface of thepiezoelectric layer 38 under the non-element region 41, which is on thepiezoelectric element 32 side, is in a state of being inclined downwardfrom the other end of the upper electrode layer 39 toward the outside.Regardless of the thickness of the piezoelectric layer 38 under thepiezoelectric element 32 (the piezoelectric layer 38 in a state wherethe over-etching is not performed), a difference OE (amount ofover-etching OE performed on the piezoelectric layer 38 under thenon-element region 41) between the thickness (average value) of thepiezoelectric layer 38 under the non-element region 41 and the thicknessof the piezoelectric layer 38 under the piezoelectric element 32 isequal to or less than 50 nm. This will be described below in detail. Inthis embodiment, since the piezoelectric layer 38 is formed of theabove-mentioned dielectric polycrystals, and the surface of thepiezoelectric layer 38 is etched by dry etching, an amorphous damagedlayer 43 is formed on the etched surface of the piezoelectric layer 38.It is preferable to ensure that the thickness of the damaged layer 43does not exceed 30 nm.

In a case where the amount of the over-etching OE to be performed on thepiezoelectric layer 38 under the non-element region 41 is set to zero,that is, in a case where the over-etching will not be performed on thepiezoelectric layer 38, the upper electrode layer 39 might remainslightly on the piezoelectric layer 38. If the upper electrode layer 39remains in a region where the upper electrode layer 39 should beremoved, a short circuit might occur between the upper electrode layer39 and a nearby piezoelectric element 32, the lead electrode layer 44,and other electrodes. In addition, damage that causes inhomogeneity ofthe upper electrode layer 39 becomes likely to occur. For this reason,it is necessary to perform the over-etching on the piezoelectric layer38 under the non-element region 41, thereby reliably removing the upperelectrode layer 39. However, it is known that the reliability of thepiezoelectric layer 38 (piezoelectric element 32) decreases if theamount of over-etching OE is excessive.

FIG. 5 is a graph illustrating a relationship between an amount ofover-etching OE performed on the piezoelectric layer 38 and a defectrate of the piezoelectric element 32 found in an endurance test. Asillustrated in the graph, the horizontal axis represents amounts ofover-etching OE (nm), and the vertical axis represents defect rates ofthe piezoelectric elements 32 found in the endurance test. A solidcircle mark represents test results obtained when the thickness of thepiezoelectric layer 38 under the piezoelectric element 32 (thepiezoelectric layer 38 in a state where the over-etching was notperformed) was set to 1300 nm, and a x mark represents test resultsobtained when the thickness of the piezoelectric layer 38 under thepiezoelectric element 32 (the piezoelectric layer 38 in a state wherethe over-etching was not performed) was set to 750 nm. In thisembodiment, in the endurance test of the piezoelectric element 32, anexamination method was used, in which the piezoelectric element 32,which was in a state of being assembled into the recording head 3,discharged the ink 100 million times from the nozzles 22 by the use of adischarging waveform, to find if defects, including a discharge defectand the like, occur. In a case where an ink discharge defect caused bydamage to the piezoelectric element 32 (piezoelectric layer 38) hadoccurred even once, the recording head 3 was counted as a defectiverecording head. The graph in FIG. 5 illustrates defect rates of therecording head 3. The maximum voltage of the discharging waveform thatwas used in the endurance test of the piezoelectric element 32 wasadjusted such that the electric field of the same strength was appliedto the piezoelectric element 32 which was interposed between the lowerelectrode layer 37 and the upper electrode layer 39 even in a case wherethe thickness of the piezoelectric layer 38 under the piezoelectricelement 32 varied.

As illustrated in FIG. 5, it can be seen that the defect rate increasedrapidly if the amount of over-etching OE exceeded 50 nm when thethickness of the piezoelectric layer 38 under the piezoelectric element32 was set to 1300 nm. It can be also seen that the defect rateincreased rapidly if the amount of over-etching OE exceeded 50 nm evenwhen the thickness of the piezoelectric layer 38 under the piezoelectricelement 32 was set to 750 nm. In other words, it can be seen that thedefect rate increased rapidly if the amount of over-etching OE exceeded50 nm regardless of the thickness of the piezoelectric layer 38 underthe piezoelectric element 32. For this reason, it is preferable to setthe amount of over-etching OE performed on the piezoelectric layer 38under the non-element region 41 to 50 nm or less. By doing so, it ispossible to prevent damage to the piezoelectric element 32 since the endof the piezoelectric element 32 is defined by the other end of the upperelectrode layer 39. As a result, the reliability of the piezoelectricelement 32 is improved, resulting in improved reliability of thepiezoelectric device 14 and improved reliability of the recording head3.

It is known that ink discharge defects occur by the piezoelectric layer38 that is in a boundary between the piezoelectric element 32 and thenon-element region 41 (the other end of the upper electrode layer 39)being damaged. It is estimated that this damage is caused by stressbeing concentrated on the piezoelectric layer 38 in the boundary betweenthe piezoelectric element 32 and the non-element region 41, minutecracks being created in the piezoelectric layer 38 due to the generationof an electric field in the boundary, and electric current flowing inthe minute cracks when moisture or the like has entered the minutecracks.

Since the minute cracks are created just by the over-etching beingperformed, it is estimated that similar damage occurs in the insulatinglayer that is interposed between the electrode layers. In other words,the damage might occur when the electric current flows in the minutecracks created by the over-etching even in a case where stress is notconcentrated on a boundary between the insulating layer and thenon-element region. It is estimated that rates of defects caused bydamage to an end of a capacitor show a similar tendency illustrated inthe graph of FIG. 5, even the capacitor is formed of a pair of upper andlower electrode layers and the insulating layer that is interposedtherebetween, since the degree of the minute cracks varies depending onthe amount of the over-etching.

Since the piezoelectric layer 38 is made of dielectric polycrystals, inthis embodiment, slight unevenness is formed, due to crystal grains, ona surface of the piezoelectric layer 38 which is in a state where theover-etching is not performed. For this reason, a short circuit mightoccur between the upper electrode layer 39 that has filled theunevenness and other electrodes when the upper electrode layer 39 is notremoved by the etching. It is preferable to have the amount of theover-etching OE performed on the piezoelectric layer 38 be larger thanat least the arithmetic average roughness (Ra) of the surface of thepiezoelectric layer 38 such that the short circuit is prevented. It iseven more preferable to have the amount of over-etching OE performed onthe piezoelectric layer 38 be larger than a mean roughness depth (Rz) ofthe surface of the piezoelectric layer 38, that is, a sum of a maximumpeak height (Rp) and a maximum valley depth (Rv) such that the upperelectrode layer 39 that has filled the unevenness of the surface of thepiezoelectric layer 38 is reliably removed.

As illustrated in FIG. 2, the sealing plate 33 is a substrate in which apiezoelectric element housing space 34 that is capable of housing thepiezoelectric element 32 is formed. The sealing plate 33 is bonded ontothe diaphragm 31 in a state where the piezoelectric element 32 is housedin the piezoelectric element housing space 34. It is possible to adopt asealing plate in a flat plate-like shape in which a piezoelectricelement housing space is not formed. In this case, a space for housingthe piezoelectric element is formed by having the thickness of adhesivethat bonds a diaphragm and the sealing plate together be large, and byenclosing the surroundings of the piezoelectric element with theadhesive. It is also possible to adopt a sealing plate having aconfiguration in which a circuit and wiring, such as a drive circuit andthe like, are provided in the sealing plate.

The recording head 3 that is formed in a manner described aboveintroduces the ink from the ink cartridge 7 into the pressure chambers30 via the liquid introduction path 18, the common liquid chamber 25,and the individual communication path 26. In this state, the drivesignal from the control unit is supplied to the piezoelectric element 32via the wiring member, thereby driving the piezoelectric element 32 tochange the volumes of the pressure chambers 30. By the use of thechanged volume and a subsequent pressure change, ink droplets areejected from the nozzles 22 that communicate with the pressure chambers30 via the nozzle communication path 27.

Hereinafter, a piezoelectric device 14 manufacturing step, specifically,a piezoelectric element 32 manufacturing step will be described. FIGS.6A to 6D are state transition diagrams illustrating the piezoelectricelement 32 manufacturing step in sections. First, the diaphragm 31 isstacked on an upper surface (surface opposing the sealing plate 33) of asilicon single crystal substrate that will become the pressure chamberformation substrate 29. Next, on the upper surface of the diaphragm 31,the lower electrode layer 37 and the piezoelectric layer 38 arepatterned sequentially by semiconductor processes (that is, a filmforming step, a photolithography step and an etching step, or the like).Once the piezoelectric layer 38 is patterned, a metal layer 39′ thatwill become the upper electrode layer 39 is made over the upper surfaceof the diaphragm 31 in the film forming step as illustrated in FIG. 6A.Then, a resistant layer made of a photosensitive resin is applied ontothe metal layer 39′, the metal layer 39′ is exposed and developedthrough a mask, and thereby a resistant layer 46 is patterned at apredetermined position (refer to FIG. 6B). In this state, the etchingstep is implemented, and the upper electrode layer 39, the leadelectrode layer 44, and the like are formed. That is, as illustrated inFIG. 6C, unnecessary parts of the metal layer 39′ are removed by theetching (dry etching, in this embodiment) with the patterned resistantlayer 46 used as a mask.

In the etching step, the piezoelectric layer 38 which is in a regionwhere the resistant layer 46 is not stacked is removed by 50 nm or lessin the thickness direction by so-called over-etching in which etching iscontinuously performed even after the removal of the upper electrodelayer 39. In particular, as illustrated in FIG. 6C, the upper electrodelayer 39 under the non-element region 41 which is on the outside of theother end of the piezoelectric element 32 is removed by the etching, andthe etching is continuously performed even after the removal of theupper electrode layer 39 under the non-element region 41, therebyremoving the piezoelectric layer 38 under the non-element region 41 by50 nm or less. Then, the resistant layer 46 is peeled off after theetching step, as illustrated in FIG. 6D. Accordingly, it is possible tomanufacture, at a high yield rate, a highly reliable piezoelectricelement 32 in which damage to the end of the upper electrode layer 39 isprevented while preventing the upper electrode layer 39 from remainingon the piezoelectric layer 38. That is, it is possible to efficientlymanufacture the piezoelectric element 32 with improved reliability,thereby efficiently manufacturing the piezoelectric device 14 ofimproved reliability, eventually.

Once the piezoelectric element 32 is manufactured on the diaphragm 31,the sealing plate 33 is bonded onto the diaphragm 31 in a state wherethe piezoelectric element 32 is housed in the piezoelectric elementhousing space 34. Lastly, in a pressure chamber forming step, thepressure chamber 30 is formed in a lower surface (surface on a side towhich the communication substrate 24 is connected) of the silicon singlecrystal substrate that will become the pressure chamber formationsubstrate 29. For example, the pressure chamber 30 is formed by etchingthe lower surface of the silicon single crystal substrate which willbecome the pressure chamber formation substrate 29. Accordingly, thepiezoelectric device 14 illustrated in FIG. 2 and the like aremanufactured.

The piezoelectric device 14 manufactured in such a manner is bonded ontothe upper surface of the flow path unit 15 (communication substrate 24).Herein, the flow path unit 15 is manufactured through a communicationsubstrate forming step in which a flow path, such as the common liquidchamber 25 and the like, is formed in a substrate (for example, asilicon single crystal substrate) that will become the communicationsubstrate 24, a nozzle plate forming step in which the nozzles 22 thatcommunicate with the pressure chambers 30 are formed in a substrate (forexample, a silicon single crystal substrate) that will become the nozzleplate 21, and a flow path unit plate forming step in which the flow pathunit 15 is formed by both of the substrates being adhered to each other.Once the piezoelectric device 14 is connected to the flow path unit 15,the head case 16 is connected to the flow path unit 15 in a state wherethe piezoelectric device 14 is housed in the housing space 17 of thehead case 16. Accordingly, the recording head 3 illustrated in FIG. 2 ismanufactured.

In the embodiment described above, the one end of the piezoelectricelement 32 in the direction orthogonal to the nozzle column direction isdefined by the one end of the lower electrode layer 37. Without beinglimited thereto, however, it is possible to adopt a configuration inwhich the one end of the piezoelectric element 32 is defined by the oneend of the upper electrode layer 39. That is, it is possible to adopt aconfiguration in which the one end of the piezoelectric element 32 isdefined by the one end of the upper electrode layer 39 which is formedon the inside of the one end of the lower electrode layer 37. Even inthis case, it is preferable to etch the piezoelectric layer under thenon-element region which is in the outside of the one end of thepiezoelectric element by 50 nm or less. In addition, in the embodimentdescribed above, dry etching is performed in the etching step. Withoutbeing limited thereto, however, it is possible to etch the upperelectrode layer 39 and the piezoelectric layer 38 by wet etching.

Hereinbefore, as an example of a type of the electronic device, thepiezoelectric device 14 provided with the piezoelectric element that isassembled into the recording head 3 has been described. However, theinvention can be provided in and applied to other electronic devicesinsofar as the electronic device includes a capacitor that has aninsulating layer which is interposed between the first electrode layerand the second electrode layer. That is, damage to a boundary between acapacitor and a non-element region of an electronic device can beprevented even if the electronic device has an over-etched non-elementregion which is on the outside of an end of the capacitor defined by oneend of the upper electrode layer 39.

In addition to the piezoelectric device assembled into the recordinghead, the invention can be applied to a piezoelectric device in whichthe piezoelectric element functions as a sensor. In addition to theliquid ejecting head, the invention can also be applied, for example, toa colorant discharging head that is used in manufacturing color filters,such as a liquid crystal display, an electrode material discharging headthat is used in forming electrodes, such as an organicelectroluminescent (EL) display, a field emission display (FED) and thelike, a bioorganic material discharging head that is used inmanufacturing biochips (biochemical elements), or the like.

What is claimed is:
 1. A piezoelectric device comprising: a diaphragm;and a plurality of piezoelectric elements, wherein each one of theplurality of piezoelectric elements is configured with a first electrodelayer, a first piezoelectric layer, and a second electrode layer beingstacked on the diaphragm in the order listed herein, wherein the firstelectrode layer is formed to be common for the plurality ofpiezoelectric elements and the second electrode layer is formedindividually for each of the plurality of piezoelectric elements,wherein the piezoelectric element is defined by a region where the firstelectrode, the piezoelectric layer and the second electrode layer arestacked, wherein the piezoelectric layer is provided so as to extend toa non-element region that is outside of the piezoelectric element,wherein the piezoelectric layer of the non-element region is formedthinner than the piezoelectric layer of the piezoelectric element in adirection intersectional to a direction which the plurality ofpiezoelectric elements are arranged, wherein a damaged layer is formedon a surface of the piezoelectric layer of the non-element region, andwherein a thickness of the damaged layer is equal to or less than 30 nm.2. The piezoelectric device according to claim 1, wherein the damagedlayer is amorphous.
 3. The piezoelectric device according to claim 1,wherein, in the direction intersectional to the direction which theplurality of piezoelectric elements are arranged, a boundary of thepiezoelectric layer of the non-element region, which is on thepiezoelectric element side, is in a state of being sloped from thepiezoelectric element.
 4. A liquid ejecting head comprising: thepiezoelectric device according to claim 1; a pressure chamber of which avolume is changed, following deformation of the piezoelectric element;and a nozzle that communicates with the pressure chamber.
 5. Amanufacturing method for a piezoelectric device including a diaphragm,and a plurality of piezoelectric elements, wherein each one of theplurality of piezoelectric elements is configured with a first electrodelayer, a piezoelectric layer, and a second electrode layer being stackedon the diaphragm in the order listed herein, the manufacturing methodfor the piezoelectric device comprising: etching the second electrodelayer to remove the second electrode layer and, in a directionintersectional to a direction which the plurality of piezoelectricelements are arranged, continuously etching the piezoelectric layer in anon-element region that is outside of a piezoelectric element defined bya region where the first electrode, the piezoelectric layer and thesecond electrode layer are stacked, such that a damaged layer of which athickness is equal to or less than 30 nm is formed on a surface of thepiezoelectric layer of the non-element region wherein the firstelectrode layer is formed to be common for the plurality ofpiezoelectric elements and the second electrode layer is formedindividually for each of the plurality of piezoelectric elements.
 6. Themanufacturing method for the piezoelectric device according to claim 5,wherein the damaged layer is amorphous.
 7. The manufacturing method forthe piezoelectric device according to claim 5, wherein, in a directionintersectional to a direction which the plurality of piezoelectricelements are arranged, a slope from the piezoelectric element is formedin a boundary of the piezoelectric layer of the non-element region,which is on the piezoelectric element side, by the etching.
 8. Amanufacturing method for a liquid ejecting head comprising: themanufacturing method for the piezoelectric device according to claim 5;forming a pressure chamber of which a volume is changed, followingdeformation of the piezoelectric element; and forming a nozzle platewhere a nozzle that communicates with the pressure chamber is formed.